38 ON THE POISONOUS ACTION OF DI-CYANOGEN. 



the fermentative action of yeast without killing it. But we have 

 found further that if the hydrocyanic acid of the same strength 

 remains in contact with yeast for more than one day, or if, in- 

 stead of hydrocyanic acid solution of 1 : 1000 a stronger solution 

 is applied, as 1 : 400, it will damage the fermentative activity so 

 much that afterwards the yeast produces only a very faint fer- 

 mentation. It seems to us that only a few yeast cells escaped 

 death under these circumstances. We have found furthermore 

 that 2 day's contact with hydrocyanic acid in a dilution of 1: 

 5000 with frequent shaking, will kill almost all the cells, so 

 that after pouring off the hydrocyanic acid, the yeast being 

 shaken up in sterilized Pasteur's solution showed only very 

 slight indications of fermentative action. 



If we compare this result with our further observation that 

 the fermentative action is not suppressed when we add to the mix- 

 ture of yeast and Pasteur's solution prussic acid in the proportion 

 of 1 : 5000, we are led to the conclusion that in all probability 

 the hydrocyanic acid upon entering the yeast cell undergoes 

 decomposition before it can act poisonously. If, however, the 

 yeast is not in fermenting activity, the entering hydrocyanic acid 

 is not so quickly decomposed, and therefore acts as a slow poison. 

 It may perhaps be assumed that the change consists in the addi- 

 tion of H 2 0, forming thereby formamid : 



HCN + H 2 0 = HCl° H2 . 



Action of Di-cyanogen and Prussic Acid 

 upon Algae. 



If threads of Spirogyra communis are treated with a solution 

 of di-cyanogen of 0.39%, instantaneous death with contraction and 

 turbidity of the cytoplasm is observed. In solutions of di-cyano- 

 gen, respectively hydrocyanic acid of 1:1000, no noxious effect 

 was seen after 30 minutes, but after 4 hours most of the cells in 

 the cyanogen solution were killed; in the prussic acid solution, 

 however, a much smaller proportion of cells. After 15 hours, all 

 the cells were dead in both cases. Also solutions of 1 : 10000 

 exerted a poisonous influence after several days I) , but it could 



1) In another case the noxious effects of the two substances in the same dilution 

 were observed after 20 hours ; on treating with very dilute methyl violet the cells 

 of the algae in the cyanogen were all coloured, but of those in the prussic acid some 

 cells not, showing these were still alive. 



